Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.77	8.329%	$124.3292	$124.33	$124.35	$124.30
Purchase #2	$225.52	7.677%	$242.8332	$242.83	$242.85	$242.80
Purchase #3	$107.27	9.342%	$117.2912	$117.29	$117.30	$117.30
Purchase #4	$109.41	6.152%	$116.1409	$116.14	$116.15	$116.10
Purchase #5	$22.50	13.288%	$25.4898	$25.49	$25.50	$25.50
Purchase #6	$133.79	4.846%	$140.2735	$140.27	$140.25	$140.30
Purchase #7	$227.38	13.827%	$258.8198	$258.82	$258.80	$258.80
7 purchase totals =	$940.64		$1,025.1776	$1,025.17	$1,025.20	$1,025.10